Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• Leping Liu Bo Xu Gerald B. Hammond Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, KY 40292, USA 10.3762/bjoc.7.71 Abstract During the last decade, gold-catalyzed reactions have become a tour de force in organic synthesis. Recently, the gold-, Brønsted acid

• carbon–carbon double bond and the simultaneous installation of a carbonyl group. In this regard, several Lewis or Brønsted acid-catalyzed intermolecular or intramolecular alkyne–carbonyl metatheses have been extensively studied (Scheme 1) [19][20][21][22][23][24][25][26][27]. During the early years of

• intermediate, which then generates an oxetenium intermediate. After several electron transfer steps, the cyclic enone product is formed. A similar [2 + 2] pathway has also been invoked for the Brønsted acid- or Lewis acid-mediated intramolecular and intermolecular alkyne–aldehyde metatheses. If terminal

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• set of conditions that fulfilled both the requirement of reaction homogeneity and reaction rate whilst at the same time providing clean and complete nitrile to tetrazole conversion involved the use of NMP as solvent, AcOH as Brønsted acid and H2O as co-solvent. Thus, 2.5 equiv of NaN3 and a 5:3:2

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• ][76] were prepared. One-pot EYCM followed by Brønsted acid catalyzed cyclization enabled the formation of monounsaturated cyclic amines [77]. The EYCM of homopropargylic tosylate with allylic alcohol derivatives has been used as a key step for the construction of the side chain of mycothiazole [78

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• benzyl azide with α,β-unsaturated imides. Using a strong Brønsted acid (triflic acid) to activate the electron deficient imide π-bond, high diastereoselection was observed provided that a 1,1,3,3-tetraisopropoxydisiloxanylidene group (TIPDS) is used to restrict the conformation of the central 1,3-anti

• alkene functionalization such as aminohydroxylation [3] and dihydroxylation [4] reactions, or by methods that forge the carbon–carbon bond such as the glycolate Mannich reaction [5]. Recently, we developed a Brønsted acid-promoted azide–olefin reaction as an alternative to metal catalyzed

Synthesis of 3-(quinolin-2-yl)- and 3,6-bis(quinolin-2-yl)-9H-carbazoles

• Yang Li and
• Wentao Gao

Beilstein J. Org. Chem. 2010, 6, 966–972, doi:10.3762/bjoc.6.108

• , the Friedländer quinoline synthesis can be achieved by the use of a variety of Brønsted acid catalysts, such as hydrochloric acid, perchloric acid, sulfuric acid, p-toluene sulfonic acid, sulfamic acid, phosphoric acid, and trifluoroacetic acid [43][44][45]. However, many of these procedures are not

Preparation of pyridine-3,4-diols, their crystal packing and their use as precursors for palladium-catalyzed cross-coupling reactions

• Tilman Lechel,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 42, doi:10.3762/bjoc.6.42

• catalytic amounts of palladium on charcoal. Methyl ethers such as 1b or 1d were cleaved by Lewis-acids. The (2-trimethylsilyl)ethyl-protected pyridine 1c was easily deprotected to diol 2c by a Brønsted acid such as TFA. In most cases, the corresponding pyridindiols 2a–d were obtained in good yields (63

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• . Despite the great importance of the Friedel–Crafts alkylation for organic synthesis it has major drawbacks since stoichiometric or super stoichiometric amounts of a Lewis acid or Brønsted acid and toxic alkyl halides have to be utilized leading to vast amounts of salt side products. With the need for more

• . However, 10 mol% of HAuCl4 had to be used (Scheme 7). The Lewis- and Brønsted acid catalyzed activation of benzyl alcohols and derivatives is not only restricted to the Friedel–Crafts alkylation and the application of arenes but can additionally be extended to other nucleophiles. In particular, mono

• subsequently developed utilizing nanostructured MoO3 (Scheme 11B) [47][48]. Recently, Kobayashi et al. reported a dehydrative nucleophilic substitution of benzyl alcohols in water employing a dodecylbenzenesulfonic acid (DBSA) as a surfactant-type Brønsted acid catalyst. With this green methodology a variety

Zeolite catalyzed solvent- free one-pot synthesis of dihydropyrimidin- 2(1H)-ones – A practical synthesis of monastrol

• Mukund G. Kulkarni,
• Sanjay W. Chavhan,
• Mahadev P. Shinde,
• Dnyaneshwar D. Gaikwad,
• Ajit S. Borhade,
• Attrimuni P. Dhondge,
• Yunnus B. Shaikh,
• Vijay B. Ningdale,
• Mayur P. Desai and
• Deekshaputra R. Birhade

Beilstein J. Org. Chem. 2009, 5, No. 4, doi:10.3762/bjoc.5.4

• has also been used recently for this purpose [35]. The Brønsted acid mediated Biginelli reactions using p-TSA [36], H2SO4/SiO2 [37], and KHSO4 [38] are known in the literature. The heterogeneous catalysts used in this reaction involve the use of KSF (montmorillonite) [39], bentonitic clay [40], and

The enantiospecific synthesis of (+)-monomorine I using a 5-endo- trig cyclisation strategy

• Malcolm B. Berry,
• Donald Craig,
• Philip S. Jones and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2007, 3, No. 39, doi:10.1186/1860-5397-3-39

• ) underwent smooth 5-endo-trig cyclisation to furnish N-(diphenylphosphinyl)pyrrolidines 5 (X = Dpp) in good yields. [3][16] Furthermore, dephosphinylation was readily achieved under either Lewis acidic or Brønsted acid conditions compatible with a range of functional groups. This second-generation

Tether- directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

• Peter J. Jervis and
• Liam R. Cox

Beilstein J. Org. Chem. 2007, 3, No. 6, doi:10.1186/1860-5397-3-6

• precursors in hand, we were ready to conduct our intramolecular allylation study. Each aldehyde substrate (>95:5 d.r. in all four cases) was treated with TMSOTf in the presence of 2,4,6-tri-t-butyl pyrimidine (TTBP), [24] which acts as a Brønsted acid scavenger, in CH2Cl2 as solvent, conditions that had